Control system for indicator projector



1965 G. VAN GELDER ETAL 3215033 GONTRL SYSTEM FOR INDIGATQR PROJECTOR Filed Sept. 14, 1962 4 Sheets-Sheet 1 INVENTR GZ EWIJN VAN GELDER WILHELMUS 1.. VERVEST HENDRIK W.D VRIES LMBERT KRIEK AGENT 1965 G. VAN GELDER ETAL 3215933 v CNTRQL SYSTEM FOR INDICATR PROJECTQR Filed Sept. 14, 1962 4 Sheets-Sheet 2 FIG.4

F Go 5 IN VENTOR GOZ EWIJN VAN GELDER WILHELMUS L.VERVEST HENDRIK W.DE VRIES LAMBERT KRIEK N0v. 1965 G. VAN GELDER ETAL 3215933 coumo1. SYSTEM FOR INDICATOR PROJECTOR Filed Sept. 14, 1962 4 Sheets-Sheet 3 F 7 NVENTOR GOZ EWIJN VAN GELDER WILHELMUS L.VERVEST HENDRIK W. DE VRIES LAMBERT KRIEK AGENT Nov. 2, 1965 G. VAN GELDER ETAL 321533 CONTRQL SYSTEM FOR INDIGATOR PROJECTOR Filed 591312. 14, 1962 4 Sheets-Sheet 4 INVENTOR United States Patent O 3,215,033 CONTROL SYSTEM FOR INDICA'IR PROJECTOR Gozewijn van Gelder, Wilhelmus Lambertus Vervest,

Hendrik Willem de Vries, and Lambert Kriek, l-Iil versum, Netherlands, assignors to North Ameriean Philips Company, Inc., New York, N.Y. a corporation of Delaware Filed Sept. 14, 1962, Ser. No. 223,675 Claims priority, applieation Netherlands, Sept. 28, 1961, 269,715

6 Claims. (Cl. 88-24) Ths invention relates to projectors for projecting an indicator sign, such as an arrow, on a sereen by means of two rotary mirrors having intersecting axes of rotation, the first mirror direeting the image of the indicator sign produced by a light souree to the second mirror which projects the sign onto the sereen, the sign being moved aeross the sereen by rotation of the mirrors about their axes. Such a projector is suitable as a help with lectures and the like, the speaker thus being able to indicate certain points on the sereen without using a stick. The projector is also suitable for use in regulating trafiie in any form by indicating, for example, the intensity of the trafiic in a given zone. T this end, a chart of the relevant zone may be projected on a greatly enlarged scale to find out by means of the projector at what points steps are necessary.

It is usually possible to project either on a spherical surface, er om a plane or curved surfaee. If projected on a flat sereen the movernent of the sign on the sereen resulting from a rotation of the second mirror does not take place along a straight line. The ray emanating from the second mirror upon rotation of this mirror describes the peripheral surface of a eone and the line followed by the sign on the sereen constitutes the intersection of the conical periphery and the sereen. If the second mirror is rotated and the first mirror remains immovable the projected sign indieates a point of a hyperbola upon projection on a plane sereen. It may be desirable for the projection sign, upon rotation of the second mirror, to describe a line differing from a hyperbola, for example a straight line. The indication of the sign diters consderably trom, for exarnple, a straight line especially at the corner points of the sereen.

An object of the invention is to correct the indication of the position of a sign which dffers from a desired indication, for example a straight line. According to the invention this is achieved in that the meehanisms for moving the mirrors are eonpled together by means of mernbers bringing about a eorrecting rotation of one mirror as a funetion of the position of the second mirror in order to obtain a prescribed movernent, for example rectilinear, of the sign projeeted on a surfaee of given shape upon rotation of the second mirror. Consequently, the position of the second mirror is a measure of the correction.

In a known embodirnent a correction is also used, it is true, but the said deviation in the position of the sign is not eliminated. It is achieved only that, if the first mirror is rotated and the second mirror rernains immovable, the path covered by the indicator sign on the screen is along a straight line proportional to the angular displacernent of the driving mechanism for the first mirror. On various straight lines (dependent upon the position of the second mirror) the path covered is in each case proportional to the angular displacement of the driving mechanism, but the absolute value is not always the same, resulting in the deviation of position.

In one embodiment of the invention the driving mechanism for the first mirror comprises a translatable part to which a rod for displaeing the mirror is movably conneeted by screw thread, said rod being provided with a transverse pin the end of which is urged against a surface eonsisting of two parts which are pivotably eonnected together and each adapted to be inclined at an angle, the angle of inclination being adjustable by means of two feeler pins operated, at one of their ends, by two cams provided on the translating part of the driving mechanism for the second mirror and engaging, at their other ends, part of the adjustable surfaces. The correction in the position of the indicator sign is obtained by a correcting dsplacernent of the first mirror. Upon rotation of the second mirror the pin on the rod follows the adjustable surfaee so that the rod is rotated and displaeed in an axial direetion due to the threaded connection, resulting in the position of the first mirror being corrected. If the second mirror remains imrnovable and the first mirror is rotated the sign deseribes a straight line on the flat sereen the position of which depends upon the position of the second mirror. Now also a correction takes place due to the pin sliding over the inclined surface and henee acting upon the first mirror. By means of this correction it is achieved that the sign, upon a given rotation of the first mirror, always covers the same path for dierent positions of the second mirror. The indicator sign thus always occupes the desired position on the sereen even if both mirrors are rotated.

In another embodiment of the projector aeeording to the invention the driving mechanism for the first mirror comprises a translatable part operating through a pivotal strip a rod rotating the mirror, said strip extending trans versely to the direetion of movement of the translating part and the rod and being displaeed by a knife edge provided on a pin journalled to be slidable transversely to the translatable part of the driving mechanism, the end of said pin being urged against a table displaceable in the direetion of height by means of a pin eonnected thereto, the end of which is urged against the surfaee of a curved guide path eonnected to the translatable part of the driving mechanism for the second mirror. In this embodiment also a correcting displaeement is imparted to the first mirror, dependent upon the position of the second mirror. The pivotal strip acts as a lever the length of one arm of which is dependent upon the knife edge which engages the lever and is adjustable in the direetion of height. The first mirror acquires the desired correction at each position of the second mirror by varation in the ratio of the lever.

It is also possible to obtain a correct position of the sign by correcting the position of the second mirror. According to the invention, to this end, the second mirror has, in addition to its first axis of rotation, a second axis of rotation which is at right angles thereto, the mirror being suspended cardanically and the suspension mechanism for the second axis of rotation being connected to an arm the free end of which has a feeler pin which may scan an arcuate surface in order to rotate the mirror about the second axis upon rotationbf the mirror about the first axis, which arcuate surface niay be moved by the driving mechanism for the firstrnirror.

In order to obtain, upon displaeernent of the translatable part of the driving mechanism with equal steps, a displacemcnt of the indicator sign across the sereen with the sarne step size, the driving mechanism for each mirror may be constituted, according to the invention, by a bolt-and-nut construction the nut of which is movable and, upon displacement, imparts a deflection to a piv otally arranged lever which causes a rotation of the mirror through a transmission gear having a transmission ratio of 1:2. Due to the transmission ratio of 1:2, the angular displaeement of the lever is equal to the angular displacement of the rays emerging from the mirror. The sign makes equal steps on the sereen by giving the lever a deflection in equal steps.

In a projector aceording to the invention the intersecting axes of rotation are preferably at right angles to one another, the axes being loeated, at least substantially, in the assoeiated planes of the mirrors. By such an arrangement it is avoided that, if the indicator sign has the shape of an arrow, the arrow on the screen is turned upon displacement of the mirrors.

The indicator sign may be in the form of an arrow, but may alternatively be built up of a combination of signs which may be eolored, if desired.

In order that the invention may be readily carried into eteet, the several embodiments thereof will now be described in detail, by way of example, with reference to the accompanying diagrammatie drawings, in which:

FIGURE 1 is a diagrarnrnatic view of the projector;

FIGURE 2 is a front elevation view of a flat projection sereen with the widths of the projected sign upon displacement of the second mirror without the use of correetion;

FIGURE 3 is a diagrammatie view of a portion of the mechanism for displacing a mirror;

FIGURE 4 is a cross-seetional view partly in elevaiton of a first embodirnent of the correcting members;

FIGURE 5 is a perspective view of this embodiment;

FIGURE 6 is an alternative embodirnent of the correcting members shown in FIG. 4;

FIGURE 6a is a diagrammatie view of the lever mechanism;

FIGURE 7 is a perspective view of the embodiment of FIG. 6a;

FIGURE 8 shows another embodiment of the con- Struction shown in FIG. 4, and

FIGURE 9 is a perspective view thereof.

In the projector shown in FIGURE 1, the light from a light source 1 is direeted through a condenser lens 2 to a rotary disc 3 which contains an indicator sign, for example in the form of an arrow, and which may be rotated in accordanee with the desired direction of the arrow. The indicator sign may alternatively be built tip of several signs or digits provided 011 transparent discs or plates positioned after one another. The horizontal beam of rays then strikes an immovable mirror 4 which turns the beam in the horizontal plane through an angle of 90 and causes it ultimately to leave the projector in its longitudinal direction. The sign is directed from mirror 4 to an objective 5 and thence to a first rotary mirror 6 which can rotate about an axis 7 and displaces the sign on the sereen in one direction, for example the horizontal direction. The beam of rays strikes mirror 6 at the centre of its axis of rotation. The ray emanating from mirror 6 impinges on a second rotary mirror 8 at a point of its axis of rotation 9 dependent upon the angular adjustment of the first mirror 6. The mirror 8 displaces the sign on the sereen in a vertieal direction. The sereen on which the sign is projeeted is indieated by 10.

The skew axes 7 and 9 may be at any arbitrary angle to one another. However, it is desrable for the axes 7 and 9 to be at right angles to one another and to be located, at least substantially, in the assoeiated planes of the mirrors. It is thus ensured that the direction of the projeeted arrow does not vary upon rotation of the mirrors.

If mirror 8 is immovable and mirror 6 is rotated about the axis 7 the sign describes a straight horizontal line on the plane sereen 10. In fact, the ray emanating trom mirror 8 is co-planar with the axis 9, which has a horizontal position in the arrangement of FIGURE 1. However, i-f the mirror 6 is immovable and mirror 8 is rotated, the line followed by the sign is usnally a vertical straight line. It is often desirable, for exarnple when projeeting on part of a map, that the sign should traverse a line of a different shape, for example a straight line, upon rotation of mirror 8. When mirror 8 is rotated about its axis 9 the ray emanating therefrom describes the peripheral surface of a cone having axis 9 as its axis of revolution. Upon projeetion on a plane sereen the sign traverses a hyperbola (see FIGURE 2) instead of a straight line so that upon vertieal adjustment, despite the immovable mirror 6, a deviation in the horizontal direction oceurs. The position of the sign on the sereen thus diiers from the position desired. Especially at the corner points of the sereen the deviation from the indication of the position of the sign may assume a magnitude which cannot be tolerated. The correeting means for this indication of position will be deseribed further hereinafter.

If the mirror is rotated in equal steps, for example by means of a step motor the distance covered by the indicator sign on the sereen during sequential equal steps will not be the same. When starting from the projection center the distance covered by the sign becomes larger upon each following step. However, it is desirable for the sign to cover the same distance upon each step. This is made possible by the transmission gear shown in FIGURE 3 which is used in a projector according to the invention. A translatable member 11 driven by the step moves a lever 12 through equal distances a. The lever acts upon gear wheels 13 and 14 with a transmission ratio of 1:2. Mirror 6 is conneeted to gear wheel 14. If lever 12 is displaeed through a distance a or an angle at the mirror rotates through an angle a/2 and the emerging ray through an angle oc. Consequently, the projeeted sign covers the same distance on the sereen upon each step a of the member 11, as may be clearly seen from FIGURE 3.

FIGURES 4 and 5 show a first embodment of correcting means as used in the projector. An electric motor (not shown) for rotating mirror 6, preferably a step motor which rotates through the same angle upon each pulse received, may drive a gear wheel 15 conneeted to a shaft 16. The end of shaft 16 has a thieker head 16a which is threaded. The head 16a is secured to one end of an elongated nut 17 which moves in an axial direction upon rotation of shaft 16. The nut ean slide in a sleeve 18 arranged co-axially thereof. A rod 19 having a thieker threaded portion 19a is conneeted to the other end of nut 17. Upon axial displacement of the nut, rod 19 follows this movement and turns a lever 21 by means of a displacing member 20 secured to the rod. To avoid any play in the serewed eonneetion, a spring 63 is provided between nut 17 and rod 19. The spring 63 is secured to nut 17 by means of a pin 64 which can move in a slot 65 of the immovable sleeve 18. This securement also ensures that nut 17 cannot rotate but is shifted only in the axial direction. The lever 21 has conneeted to it a gearwheel 22 which meshes with a gear wheel 23. The transmission ratio of the gear wheels is 1:2. Mirror 6 is secured to gear wheel 23.

The driving means for the second mirror comprise a second step motor which causes rotation of a shaft 25 through a gear wheel 24. The shaft 25 has, at its end, a thieker portion 26 which is threaded and provided in an elongated nut 27. Upon rotating the shaft 25 the nut undergoes a translating movement through the same distance upon each step of the motor. The end of nut 27 is provided with a pin 28 for displacing a lever 29. This lever causes a rotation of gear wheels 30 and 31 with a transmission ratio of 1:2, thus rotating the second mirror 8 secured to gear wheel 31.

The thieker portion of rod 19 provided in nut 17 has a transverse pin 32 which projects to the exterior through an aperture of sleeve 18. The pin 32 is thrust by means of a reslient member against a surface comprising two pa rts 33 and 34 which are conneeted to a hinge 35, fixedly arranged in the projector, and which may be ad justed in inelined positions. The angles of inelination of the surfaee parts are adjusted by means of pins 36 and 37 arranged to be slidable in a block 38 forming part of the housing of the projector. The pins bear, at one of their ends, against the lower sides of the surfaces 33 and 34 and, at their ether ends, against carns 39 provided on the nut 27 of the displaeing mechanism for the second mirror. The surfaces 33 and 34 are thrust against the pins by means of springs.

If the second mirror is rotated due to translation of nut 27 the threaded portion 26 causes an axial displacement of nut 27, resulting in the cams 39 also being displaced through the same distance. Consequently, the pins 36 and 37, which keep in engagement with the eams due to the pressure of the springs, move downwards in block 38, thus giving the surfaees 33 and 34 inclined positions dependent upon the displacement of nut 27. The pin 32 will follow the movement of the surface (see FIG- URE 5) so that rod 19 is rotated. Due to the screwed connection between the rod 19 and the nut 17, rod 19 is displaeed in an axial direction and imparts a eorrecting displacement to mirror 6 through lever 21 and gear wheels 22 and 23. By suitable shaping of the earns the deviation of the sign in a horizontal direction due to the traversal of a hyperbola When mirror 8 displaces the sign in a vertical direction will be eorreeted by the correcting rotation of mirror 6 which determines the horizontal position of the sign. Ths correcting rotation of mirror 6 thus depends upon the position of mirror 8. Upon rotation of mirror 8, the sign now deescribes the desired line on the sereen due to the correction imparted to mirror 6 by rod 19. If mirror 8 is immovable and mirror 6 is rotated due to a rotation of the threaded portien of rod 16 which displaces nut 17, pin 32 slides over the inclined surface 33, 34 and thus causes a rotation of rod 19. Mirror 6 thus acquires a eorreetng rotation in addition to its rotation as a result of the axal displacement of nut 17. By the use of the transmission gear shown in FIGURE 3, the sgn eovers the same distance en a horizontal line upon each step. However, the distances covered by the sign on lines located at different heights are diflerent. Due to the said correcting rotation of mirror 6 it is ensured that the step distance of the sign is the same on all horizontal lines located at different heights (dependent upon the position of mirror 8). Upon a eombined rotation of mirrors 6 and 8 the sign is therefore always projected on the sereen in the correct position.

FIGURE 5 shows the correcting members upon displacement of the eams 39 and a resulting inelined adjustrnent of the surfaces 33 and 34. If mirror 6 is placed at an angle of 45 the surfaces 33 and 34 will be aligned and correction does not occur snce the sign then describes a vertieal line across the middle of the sereen upon rotation of mirror 8 (see FIGURE 2).

FIGURES 6, 6a and 7 show a second embodiment of the correeting members. In this case also bolt-and-nut eonstructions driven by step motors are used for rotating the mirr'ors. A rod 41 is not connected directly to a nut 40 but is displaced by means of a slidable pin 42 provided at the end of nut 40 transversely to the direction of movement thereof, pin 42 having a knife edge 43 which rnay operate a strip 44. Ths strip engages the end of rod 41 and is pivotally eonneeted to a block 45 fixedly arranged in the housing of the projector. Strip 44 must preferably have a shape such that its pivot and the points of applieation of knife edge 43 and rod 41 are aligned. To this end, strip 44 may be made, for example, very thin. Mirror 8 is rotated by means of a nut 46 which operates a lever 47 and gear wheels 48 and 49, thus causing a rotation of mirror 8 about its axis 9. Nut 46 has a curved guide path 52 which can move back and forth with the nut. The pin 42 provided in nut 40 beurs, at its end remote from knife edge 43, on a tahle 50 which is adjustable in the direction of height and can be slidably moved in block 45 by means of a pin 51. At its 5 end remote trom table 50, pin 51 has a feeler engaging the guide path 52. A spring 60 prevents nnwanted move- Inent of pin 42 and thrusts pin 51 against the guide path,

If mirror 8 is immovable and mirror 6 is rotated nut 40 is displaced and knfe edge 43 of pin 42, whidh pin slides over table 50, moves the lever 44. Ths stripshaped lever influences rod 41, thus giving mirror 6 the desired defleetion. Since strip 44, als shown in FIG- URE 6a, assumes an inclin ed position upon axial displaeement of nut 40, the rod 41, if mirror 8 is not adjusted at an angle of 45 (whereby knife edge 43 and rod 41 would be located at the same height, instead of being displaced through the same distarice as is nut 40) acquires a correcting displacernent difiering trom that of nut 40 due to the lever action of strip 44, thus en suring that the sign always covers the same distance upon each step along a1l horizontal lines folloWed which diler in height. Upon translation of mm 46 the g-uide path 52 is also displaced, thus causing table 50 to move in the direction of height. The knife edg 43 now influences strip 44 in a point loeated higher so that a correcting rotation eliminating the hyperbolic distorton is impzirted to mirror 6. This correcting transmission is shown diagramm-atically in FIGURE 6d. By dis placement of guide path 52, pin 42 will always act Upon -another point of the lever 44, which thus acquires another slope so that a matched correction of mirror 6 is obtained for eaeh a-djustment of mirror 8 and the projected sign indicaties the desired position on the sereen.

FIGURES 8 and 9 show a third embodiment of the correeting means used in the projector. In this embodi ment the correcting rotation is imparted to mirror 8, which for this purpose may rotate not only about its axis 9 but also about an axis 53 which is at right angles thereto. T0 this end, mirror 8 is secured to a spport 55 which is suspended eardanically in a helder 56 by means of pins 54. Support 55, which is rotatable about axis 53, has secured to it an arm 57 which projects to the exterior through an aperture in helder 56. The end of arm 57 is provided with a feeler pin 58 which is urged, for example by means of a spring, against an areuate surface 59 to scan this surface. The areuate surfaee 59 has a n-ut-like portion which engages in a threaded portion 62 provided on a shaft 61 of the driving mechanism for mirror 6. Upon rotation of the driving meehanism for mirror 6 the areuate surface 59 is displaced with respect to feeler pin 58. If mirror 8 is deflected a'bout its axis of rotation 9 the arm 57 is forced to follow this movement and feeler pin 58 will describ a path over the arcuate surface 59. The feeler pin is displaced in the direction of height and thus eases a displaeement of support 55. Ths support causes a rotation of mirror 8 abo-ut axis 53, at right angles to the axis of rotation 9. This r-otation provides a correction in horizontal direction of the sign projected on screen 10. Mirror 8, when deflected about axis 9, acquires a eertain correction about axis 53, dependent upon the shape of the areuate surface, thus eliminatng the incorrect indcation of the position of the sign on the sereen. If mirror 8 is immovable and mirror 6 is rotated, mirror 8 is also deflected about axis 53 since the areuate surfaee 59 is moved by means of the threaded portion 62. Ths deflection in turn ensures that, if mir ror 6 is driven in a stepwise manner, the projected sign oevers equal distances on the sereen along any horizontal line.

The shape and the position of the correcting members may be ether caleulated, or determined experimentally and depend upon the desired eo-ordinates and hence upon the question as to whether the indicator sign, upon rotation of mirror 8, de-scribes a straight line 01 a curved line of desired shape on the sereen. The shape of the projection screen is also of influence. In the embodiments described use was made of a plane sereen, but it is also p0ssible for the sereen to have a curved surfaee. Instead of nsing the bolt-and-nnt eonstruetion, the deviees for rotating the mirrors rnay alternatvely ntilize other means which convert a rotation into a translation.

It is possible to use a plurality of projectors eaeh direeting -an indicator sign to the sereen so as to enable, for example, the route of a plurality of road users or groups of road users to be followed.

What is claimed is:

1. A system for eontrolling the movement of a projected image on a sereen created by a light source eom prising two spaeed mirrors, driving means for rotating said mirrors, one of said mirnors direetin-g said projected image produced by said light source to the other mirror which in mm projects the image on the sereen, said image being moved across said sereen by the rotation of said mirrors about their axes, means eoupling said mirrors together whereby the rotation of either mirror is correeted as a funeti-on of the angular position of the other mirror in order to obtain a prescribed movement of the image npon said sereen of a given shape when said other mirror rotates.

2. A system for eontrolling the movem'ent of a projected image on a sereen created by a light source as cl-aimed in claim 1 wherein said means for rotating said one mirror eomprises a part adapted fo reetilinear movement, a rod, means conneeted to one end of said rod and said mirror for rotating the same, -a serewthreaded element movably eonneeted to said rod, said rod being provided with a transverse pin, two elements pivotally eonneeted together and eaeh adapted to be inclined at an angle, the free end of said transverse rod being in engagement with one of said pivoting elements, two eeler pins eaeh operatively engagng at one end a surfaee of one of said elements, a translating device for said other mirror having a pair of eams thereon, and the other ends of said feeler rods engaging said eams on said translating device te thereby elevate and lower said feeler rods.

3. A system for eontrolling the movement of -a projected image on a sereen created by a light source as claimed in claim 1 wherein said other mirror has two axes of rotation at right angles to one another, a suspension system for said other mirror and said sec-nd axis of rotation, an arm eonneeted at one end to said suspension system and having a feeier pin at the free end thereof, said driving means for said =one mirror hav ing -ar1 areuate snrfaee, said feeler pin engaging said ar cuate surfiaee and being movable thereover whereby said other mirror is rotated about its second axis npon rotation of the same about its first axis, said arenate surfaee being moved by said driving means for said one mirror.

4. A system for eontrolling the movement of a projected image on a sereen created by a light source comprising two spaeed mirrors, driving means for rotating said mirrors, one of said mirrors direeting said projected image produced by said light source to another mirror which in turn projects the image on the sereen, said image being moved across said sereen by the rotation of said mirrors about their axes, means eoupling said mirrors together whereby the rotation of either mirror is eorrected as a funetion of the angular position of the other mirror in order to obtain a prescribed movement of the image npon said sereen of a given shape when said other mirror rotates, said means for rotating said one mirror comprising a part adapted for rectilinear movement, a pivotable strip, and a rod eoaetng with said part and pivotal strip to rotate said one mirror, a pin extending substantially transverse to the direction of movement of said part adapted for reetilinear movement, said pin having a knife edge which engages said pivotable strip to thereby displaee said rod, a table slideable in the direction of its height, a projeetion on said table, a translatable drive mechanism for said other mirror having an inclined surfaee, said projeetion en said table engaging said inclined surface and when said drive mechanism moves said pin and knife edge are moved which in turn moves said rod to rotate said one mirror.

5. A system for eontrolling the movement of a projected image on a sereen created by a light source comprising two spaeed mirrors, driving means for rotating said mirrors, one of said mirrors directing said projected image produced by said light source to another mirror which in turn projects the image on the sereen, said image being moved across said sereen by the rotation of said mirrors about their axes, means eoupling said mirrors together whereby the rotation of either mirror is eorrected as a fnnetion of the angnlar position of the other mirror in order to obtain a preseribed movement of the image npon said sereen of a given shape when said other mirror rotates, said strip extending transversely to the direction of movement of said part adapted for rectilinear movement, and said inclined surfaee being a eurved guide path for said projeetion.

6. A system for eontrolling the movement of a projected image on a sereen created by a light source comprising two spaeed mirrors, driving means for rotating said mirrors, one of said mirrors directing said projected image produced by said light source to another mirror which in turn projects the image on the sereen, said image being moved across said sereen by the rotation of said mirrors about their axes, means eoupling said mirrors together whereby the rotation of either mirror is correeted as a fnnetion of the angular position of the other mirror in order to obtan a prescribed movement of the image npon said sereen of a given shape when said other mirror rotates, a pivotaliy arranged lever and a transmission gear wherein the driving means for eaeh mirror eomprises a bolt and nnt eonstruction, the nnt of which is movable and which, npon displaeement, imparts a defleetion to said pivotally arranged lever which eauses a rotation of the eorresponding mirror through said transmission gear havng a transmission ratio of 1:2.

References Cited by the Examiner UNITED STATES PATENTS 2,714199 7/55 Adams et al. 88--24 NORTON ANSHER, Prmary Examiner.

EMIL G. ANDERSON, Examiner. 

1. A SYSTEM FOR CONTROLLING THE MOVEMNT OF A PROJECTED IMAGE ON A SCREEN CREATED BY A LIGHT SOURCE COMPRISING TWO SPACED MIRRORS, DRIVING MEANS FOR ROTATING SAID MIRRORS, ONE OF SAID MIRRORS DIRECTING SAID PROJECTED IMAGE PRODUCED BY SAID LIGHT SOURCE TO THE OTHER MIRROR WHICH IN TURN PROJECTS THE IMAGE ON THE SCREEN, SAID IMAGE BEING MOVED ACROSS SAID SCREEN BY THE ROTATION OF SAID MIRRORS ABOUT THEIR AXES, MEANS COUPLING SID MIRORS TOGETHER WHEREBY THE ROTATION OF EITHER MIRROR IS CORRECTED AS A FUNCTION OF THE ANGULAR POSITION OF THE OTHER MIRROR IN ORDER TO OBTAIN A PRESCRIVED MOVEMENT OF THE IMAGE UPON SAID SCREEN OF A GIVEN SHAPE WHEN SAID OTHER MIRROR ROTATES. 